Self-clamping wrench

ABSTRACT

A self-clamping wrench has one fixed clamping jaw, which is rigidly connected to a handle and one mobile clamping jaw, which is mounted thereon in such a way that it can turn. A hand lever is located on the handle on the same side as the mobile clamping jaw. A leaf spring, which is fixed on the hand lever, acts upon the mobile clamping jaw and when the hand lever is closed, forms a tension spring which pushes said clamping jaw into its closed position. When the hand lever is released, the leaf spring acts as a lever spring, which opens the hand lever and the mobile clamping jaw.

BACKGROUND OF THE INVENTION

The invention relates to a self-clamping wrench having a fixed clampingjaw, which is rigidly connected to a handle, and a mobile clamping jaw,which is pivotally mounted thereon whereby said mobile clamping jaw ispushed into its closed position by a tension spring. A spring-loadedhand lever is pivotally mounted to the handle, which engages the mobileclamping jaw.

Self-clamping wrenches are well known in a great number of variousconfigurations. They have in common that the moment (torque) exerted onthe workpiece during actuation of the wrench increases the tensioningforce of the mobile clamping jaw. Such self-clamping wrenches aredesigned, for example, as spanner wrenches or pipe wrenches.

During manipulation of the wrench there is the need that the mouth ofthe wrench, which is formed between the fixed clamping jaw and themobile clamping jaw, is kept open against the effects of the tensionspring when the wrench is placed on the workpiece or when it is removed.During adjustment of the wrench between subsequent turning movements itis often times also an advantage if the mouth of the wrench can beopened against the effect of the tension spring, for example, to preventdamage to sensitive workpieces in case of toothed clamping jaws as, forinstance, in plumbing or in the use on bolts made of synthetic material.

On a known self-clamping wrench of the type mentioned in the beginningand as disclosed in U.S. Pat. No. 4,616,534, there is for this purpose ahand lever mounted on the handle at the opposite side of the mobileclamping jaw, which may be pushed toward the handle against the force ofthe lever spring. An arm of the lever engages thereby a protrusion onthe mobile clamping jaw facing the handle to swing said clamping jawinto an open position and to keep it open. The self-clamping function ofthe mobile clamping jaw is activated by the effect of the tension springonly when the hand lever is released.

Manipulation of this wrench is relatively complicated since the hand(operating) lever must be moved and held in place against the force ofits lever spring to open or keep open the mouth of the wrench. Shouldthe hand lever be released unintentionally during the use of the wrench,for example during re-gripping between two subsequent turning movements,then the mount of the wrench closes shut. This is disturbing during theoperation of the wrench and it may cause damage to sensitive workpieces,particularly when toothed clamping jaws are used.

On another known wrench (disclosed in DE-A-1 299 570), which is notself-clamping, a hand lever mounted on the handle is used to close themouth of the wrench in a movement similar to that of pliers until itgrasps the workpiece and then locks the slidable—but notpivotable—mobile clamping jaw with a cam that is joined to the handlever. The transmission of motion between the hand lever and the mobileclamping jaw is caused by a leaf spring that is attached to the handlever, which engages a recess on the mobile clamping jaw that faces thehandle.

On another known closed-end jaw wrench, disclosed in U.S. Pat. No.4,594,922, the handle lever mounted on the handle body is used to move apivotable closed-end jaw into a clamping position. The hand lever has tobe held in place by a locking device. A tension spring does not exist topush the closed-end jaw into the clamping position by the force of aspring.

The object of the invention is to design a self-clamping wrench of thetype mentioned in the beginning whereby it can be manipulated in asimple manner and whereby the self-clamping effect occurs only when thewrench is placed on the workpiece for the performance of a moment(torque); otherwise, the mouth of the wrench should open automaticallyand should remain in an open position.

SUMMARY OF THE INVENTION

This object is achieved according to the invention in that the handlever is disposed on the same side of the wrench as the mobile clampingjaw and whereby said hand lever is moved by the force of the spring in aposition that keeps the mobile clamping jaw in an open position.

This arrangement of the hand lever makes possible that said hand leveris actuated in an ergonomically favorable manner if at the same time atorque is to be applied onto the workpiece by the wrench. The hand,which grasps the handle to apply torque to the workpiece, moves therebythe hand lever automatically toward the handle without additionalactuating measures, and effects thereby the force of the tension spring,which in turn pushes the mobile clamping jaw into it closed position.Should the hand be moved away from the handle, the hand lever swingsaway from the handle as well and opens the mouth of the wrench. The handlever is kept in a position by the force of the spring in which is alsokeeps the mouth of the wrench open against the force of the tensionspring. The mobile clamping jaw will resume its self-clamping closedposition under the force of the tension spring only when the hand leveris moved again toward the handle.

According to one embodiment of the invention it is proposed that thehand lever is designed as a double-armed lever whereby its one armengages a recess on the mobile clamping jaw facing the handle andwhereby the hand lever is moved into a position holding the mobileclamping jaw open by a lever spring. The lever spring is designedthereby in such a manner that it overcomes the force of the tensionspring and the tension spring becomes subsequently effective and movesthe mobile clamping jaw in the direction of its self-clamping closedposition only when the effect of the lever spring is stopped byactuating the hand lever.

The tension spring may be attached to the handle or the hand lever. Itmay engage the recess or a slot on the mobile clamping jaw that facesthe handle.

Additional advantageous configurations of the embodiment are an objectof further minor claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments are described in more detail below with referenceto the drawings in respective longitudinal cross-sectional views:

FIG. 1 shows a wrench in an open position with a leaf spring thatengages a slot in the mobile clamping jaw whereby said leaf spring isattached to the hand lever.

FIG. 2 shows a wrench according to FIG. 1 in a closed clamping position.

FIG. 3 shows a wrench with two leaf springs, which are attached to thehand lever and which engage the mobile clamping jaw.

FIG. 4 shows an arm of the hand lever that engages the mobile clampingjaw and it also shows a leaf spring.

FIG. 5 shows a modified version of FIG. 4.

FIG. 6 shows an additional modified version.

FIG. 7 shows a wrench having a single leaf spring, which is attached tothe hand lever and which engages a contact surface on the mobileclamping jaw.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

The self-clamping wrench in FIG. 1 and FIG. 2, illustrated in arespective open or closed position, is provided with a fixed clampingjaw 1, which is rigidly connected to a handle 2. A mobile clamping jaw 3is mounted at a joint 4 between the fixed clamping jaw 1 and the handle2. The toothed clamping surface of the fixed clamping jaw 1 and themobile clamping jaw 3 shown in the embodiment example are arrangedrelative to the pivoting axis formed by the joint 4 in such a mannerthat the wrench exerts a self-clamping force on the workpiece duringactuation.

A hand lever 5 is mounted between the joint 4 and the handle 2 wherebysaid hand lever is disposed on the same side of the handle 2 as themobile clamping jaw 3. A leaf spring 6 is attached with one of its endsto the hand lever 5 near its lever joint 7, it is preferably riveted toit and engages with its free end 6 a the slot 8 of the mobile clampingjaw 3 that is facing the handle. Depending on the respective position ofthe hand lever 5, the leaf spring 6 acts either as a tension spring thatmoves the mobile clamping jaw 3 in the direction of its closed position,or it is a lever spring that keeps open the hand lever 5 and the mobileclamping jaw 3.

Should the hand lever 5 be released, then the pre-tensioned force of theleaf spring 6 causes the hand lever 5 to move into the open position asshown in FIG. 1. However, the leaf spring 6 also moves at the same timethe mobile clamping jaw 3 into its open position. The wrench can behandled in this position whereby the mouth of the wrench does not closeby itself. In particular, the wrench with its open mouth may be placedor removed from the workpiece or reset on the workpiece between twosubsequent turning movements.

Should the hand lever 5 be placed against the handle 2, as shown in FIG.2 (this position is considered “closed” in this connection), then theleaf spring 6 swings the mobile clamping jaw in the direction of itsclosed position and acts simultaneously as a tension spring to hold themobile clamping jaw against the workpiece in its closed position by theforce of the spring. The closing of the hand lever 5 is performed in anergonomically simple manner in that the handle 2 and the hand lever 5are grasped by hand to effect a moment (torque) on the workpiece(clockwise in FIG. 2). When the force on the handle 2 and the hand lever5 is released at the end of a turning movement, then the hand lever 5 aswell as the mouth of the wrench move into an open position; all partssubsequently return again to the open position as shown in FIG. 1. Thetension spring for the mobile clamping jaw 3 and the spring for the handlever 5 are hereby in form of the leaf spring 6, which is attached tothe hand lever 5 and which engages the mobile clamping jaw 3 in alongitudinal direction.

The embodiment in FIG. 3 differs from the described embodiment examplein that two leaf springs 8 and 9 are attached to the hand lever 5, whichfree ends 8 a or 9 a engage both sides of a toe 10 on the mobileclamping 3 facing the handle. The two leaf springs 8 and 9 act therebyas a tension spring for the mobile clamping jaw 3 and also as a springfor the hand lever 5.

The embodiment examples in FIGS. 4, 5 and 6, respectively have in commonthat the hand lever 5 is designed as a double-armed lever, which engageswith one lever arm 5 a the toe 10 of the mobile clamping jaw 3 facingthe handle to move said clamping jaw into its open position while thelever is also in an open position.

In the example in FIG. 4 and FIG. 5, a leaf spring 1, which is attachedto the hand lever 5 and which engages the toe 10 opposite the lever arm5 a, acts as a tension spring that pushes the mobile clamping jaw 3 inthe direction of its closed position. A lever spring, which is designedin FIG. 4 as a pressure spring 12 and in FIG. 5 as a pull-type spring13, moves the hand lever 5 into its open position whereby the force ofsaid lever spring is so great that it overcomes the force of the tensionspring 1. Thus, the open position of the hand lever 5 and the mobile jaw3 are the inoperative position of the wrench.

The embodiment example in FIG. 6 differs thereby only by the fact that apull-type spring 14, which is mounted on the handle part and which isconnected to the mobile clamping jaw 3, acts as the tension spring. Apull-type spring 14, which works similar between the handle part and thelever arm 5 a, as shown in example in FIG. 5, acts as the lever spring.The force of the lever spring 13 is here also so great that it overcomesthe force of the tension spring 14 in the released condition of thewrench, so that the mobile clamping jaw 3 is held in its open positionuntil the hand lever 5 is pushed into a closed position and the force ofthe lever spring 13 is thereby cancelled.

In the embodiment example shown in FIG. 7, the mobile clamping jaw 3 isprovided with two jaw extensions 3 a, which both engage a middle segment2 a of the handle piece. A leaf spring 15 is attached to the hand lever5 at a distance from the pivoting axis of the hand lever 5 (which axisis formed by the joint 7) in such a manner that the free end 15 a ofsaid leaf spring is moved during closing of the hand lever 5 in alongitudinal direction relative to the wrench whereby it effects anopening moment on the mobile clamping jaw 3 when the hand lever 5 isopen, and a closing moment when said hand lever is closed.

In the illustrated embodiment example, the leaf spring 15 is attached tothe hand lever 5 on the side facing away from the handle 2 and engageswith its free end 15 a a contact surface 16 of the mobile clamping jaw 3between the two extensions 3 a. The leaf spring 15 is preferably bracedwith its middle segment against the top side of the segment 2 a of thehandle piece. The contact surface 16 is offset opposite the pivotingaxis, which is formed by the joint 4, in the direction toward the mobileclamping jaw 3. The free end 15 a of the leaf spring 15 engages in thearea of the pivoting axis (joint 4) the contact surface 16 in such amanner that the point of engagement, while the hand lever 5 is open, islocated in the direction toward the mouth of the wrench and in front ofthe pivoting axis of the joint 4 and thereby effects an opening momentonto the mobile clamping jaw 3. Should the hand lever 5 be closed, thenthe point of engagement of the free end 11 a moves toward the handle 2and behind the pivoting axis of joint 4. This has the effect that amoment (torque) is created, which is directed counter-clockwise relativeto FIG. 7 and which pushes the mobile clamping jaw 3 into its locked orclosed position.

The leaf spring 15 acts thereby also as the tension spring for themobile clamping jaw 3 and as the lever spring for the hand lever 5.Depending on the position of the hand lever 5, the force of the tensionspring that closes the clamping jaw 3 is preponderant and so is theforce of the lever spring that opens the hand lever 5 and thereby alsothe clamping jaw 3.

What is claimed is:
 1. A self-clamping wrench comprising: a fixedportion including a handle and a fixed clamping jaw attached thereto; amobile clamping jaw disposed on one side of the fixed portion andpivotably mounted to the fixed portion for swinging movement toward andaway from the fixed clamping jaw between closed and open positions,respectively; and an actuating portion including: a hand lever disposedon the same side of the fixed portion as the mobile clamping jaw andpivotably mounted to the fixed portion for swinging movement between anopen position for opening the mobile clamping jaw, and a closed positionfor closing the mobile clamping jaw, and a spring arrangement forapplying a biasing force for biasing the mobile clamping jaw and thehand lever toward their respective open positions, wherein said springtransmits a jaw-closing force from the hand lever to the mobile jaw inresponse to the hand lever being swung toward its closed positionagainst the biasing force.
 2. The self-clamping wrench according toclaim 1 wherein the spring arrangement comprises a single spring forboth applying the biasing force and transmitting the jaw-closing force.3. The self-clamping wrench according to claim 2 wherein the singlespring comprises a leaf spring.
 4. The self-clamping wrench according toclaim 3 wherein a first end of the leaf spring is fixed to the handlever and a second end of the leaf spring abuts the mobile clamping jaw.5. The self-clamping wrench according to claim 4 wherein the second endof the leaf spring is disposed in a slot formed in the mobile clampingjaw.
 6. The self-clamping wrench according to claim 4 wherein the secondend of the leaf spring slides along a contact surface of the mobileclamping jaw in response to swinging of the hand lever, whereby thesecond end of the leaf spring engages the contact surface at a firstlocation thereon for biasing the mobile clamping jaw toward its openposition when the handle lever is in its open position, and engages thecontact surface at a second location thereon for biasing the mobileclamping jaw toward its closed position when the hand lever is in itsclosed position.
 7. The self-clamping wrench according to claim 6wherein the first end of the leaf spring engages a side of the handlever facing away from the handle; a portion of the leaf spring disposedbetween the first and second ends of the leaf spring engaging a surfaceof the fixed portion which faces toward the contact surface of themobile clamping jaw.
 8. The self-clamping wrench according to claim 1wherein the spring arrangement comprises a pair of leaf springs, eachleaf spring including first and second ends, the first ends being fixedto the hand lever, and the second ends engaging the mobile clamping jaw.9. The self-clamping wrench according to claim 8 wherein the mobileclamping jaw includes a toe extending generally toward the hand lever,the first ends of the leaf springs engaging opposite respective sides ofthe toe.
 10. The self-clamping wrench according to claim 1 wherein themobile clamping jaw includes a toe extending generally toward the handlever, the handle lever being pivotably connected to the fixed portionintermediate first and second ends of the hand lever, the second end ofthe hand lever arranged to contact the toe to apply a jaw-opening forceto the toe in response to the hand lever being biased open by the springarrangement.
 11. The self-clamping wrench according to claim 10 whereinthe spring arrangement comprises a first spring for applying the biasingforce and a second spring for transmitting the jaw-closing force. 12.The self-clamping wrench according to claim 11 wherein the second springcomprises a leaf spring.
 13. The self-clamping wrench according to claim12 wherein one end of the leaf spring is fixed to the hand lever, and asecond end of the leaf spring engages a side of the toe opposite to aside thereof engaged by the second end of the hand lever.
 14. Theself-clamping wrench according to claim 1 wherein the spring arrangementcomprises a first spring for applying the biasing force and a secondspring for transmitting the jaw-closing force.
 15. The self-clampingwrench according to claim 14 wherein the second spring comprises a leafspring.
 16. A self-clamping wrench comprising: a fixed portion includinga handle and a fixed clamping jaw attached thereto; a mobile clampingjaw disposed on one side of the fixed portion and pivotably mounted tothe fixed portion for swinging movement toward and away from the fixedclamping jaw between closed and open positions, respectively; and anactuating portion including: a hand lever disposed on the same side ofthe fixed portion as the mobile clamping jaw and pivotably mounted tothe fixed portion for swinging movement between a first position foropening the mobile clamping jaw, and a second position for enabling themobile clamping jaw to be closed, a first spring acting between thefixed portion and the clamping jaw for continuously biasing the clampingjaw toward its closed position, and a second spring acting between thefixed portion and the hand lever for continuously biasing the hand levertoward its first position for opening the clamping jaw, the secondspring being stronger than the first spring so that the clamping jaw isnormally biased into its open position, the clamping jaw being movableto its closed position by the first spring in response to the handlebeing manually swung to its second position.